Early Back-to-Africa Migration into the Horn of Africa
Early Back-to-Africa Migration into the Horn of Africa
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DOI：
10.1371/journal.pgen.1004393
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发表时间：
2014-06-01
期刊：
影响因子：
4.5
通讯作者：
Raaum, Ryan L.
中科院分区：
文献类型：
--
作者：
Hodgson, Jason A.;Mulligan, Connie J.;Raaum, Ryan L.
基因研究已发现非洲之角 (HOA) 存在大量非非洲混合物。在最近的基因组研究中，这种非非洲血统被归因于过去几千年与中东人群的混合。然而，线粒体和 Y 染色体数据暗示了早期的混合事件。为了进一步研究这一点，我们为也门人群样本生成了新的全基因组 SNP 数据，并将这些新数据与 HOA 和广泛选择的周围人群已发表的全基因组遗传数据合并。我们在探索性数据分析中使用多维标度和 ADMIXTURE 方法来提出有关 HOA 群体中的混合和群体结构的假设。这些分析表明，HOA 中可能存在独特的、有区别的非洲和非非洲血统。将 SNP 数据划分为非洲和非非洲起源染色体片段后，我们发现 HOA 人群中存在独特的非洲（埃塞俄比亚）血统和独特的非非洲（埃塞俄比亚-索马里）血统。非洲埃塞俄比亚血统严格限于 HOA 人群，并且可能代表本土 HOA 人群。 HOA 中的非非洲血统主要归因于新的埃塞俄比亚-索马里推断血统成分，与北非、黎凡特和阿拉伯半岛所有邻近的非非洲血统显着不同。埃塞俄比亚-索马里血统存在于所有混合的 HOA 族群中，在这些族群内几乎没有表现出个体间差异，估计与所有其他非非洲血统的差异至少为 23 ka，并且不携带大约 4 ka 出现的独特的阿拉伯乳糖酶持久性等位基因。考虑到已发表的线粒体、Y染色体、古气候和考古数据，我们发现埃塞俄比亚-索马里人返回非洲的迁徙时间很可能是前农业时代。
Genetic studies have identified substantial non-African admixture in the Horn of Africa (HOA). In the most recent genomic studies, this non-African ancestry has been attributed to admixture with Middle Eastern populations during the last few thousand years. However, mitochondrial and Y chromosome data are suggestive of earlier episodes of admixture. To investigate this further, we generated new genome-wide SNP data for a Yemeni population sample and merged these new data with published genome-wide genetic data from the HOA and a broad selection of surrounding populations. We used multidimensional scaling and ADMIXTURE methods in an exploratory data analysis to develop hypotheses on admixture and population structure in HOA populations. These analyses suggested that there might be distinct, differentiated African and non-African ancestries in the HOA. After partitioning the SNP data into African and non-African origin chromosome segments, we found support for a distinct African (Ethiopic) ancestry and a distinct non-African (Ethio-Somali) ancestry in HOA populations. The African Ethiopic ancestry is tightly restricted to HOA populations and likely represents an autochthonous HOA population. The non-African ancestry in the HOA, which is primarily attributed to a novel Ethio-Somali inferred ancestry component, is significantly differentiated from all neighboring non-African ancestries in North Africa, the Levant, and Arabia. The Ethio-Somali ancestry is found in all admixed HOA ethnic groups, shows little inter-individual variance within these ethnic groups, is estimated to have diverged from all other non-African ancestries by at least 23 ka, and does not carry the unique Arabian lactase persistence allele that arose about 4 ka. Taking into account published mitochondrial, Y chromosome, paleoclimate, and archaeological data, we find that the time of the Ethio-Somali back-to-Africa migration is most likely pre-agricultural.